Mobile Accessibility Guidelines for JSON Viewing Apps

Building mobile applications that display structured data like JSON can be challenging. Ensuring these apps are accessible to everyone, including users with disabilities, is crucial. This guide outlines key accessibility considerations specifically for mobile JSON viewing applications.

Content Presentation and Visuals

How JSON data is displayed is fundamental to accessibility. Raw JSON can be difficult to parse visually, especially for users with cognitive disabilities, low vision, or dyslexia.

Syntax Highlighting and Formatting

Applying syntax highlighting (coloring keys, values, primitives) makes the structure much easier to understand at a glance. This should be implemented with sufficient color contrast.

• Color Contrast: Ensure text and background colors meet WCAG AA or AAA contrast ratios. This is vital for users with low vision or color vision deficiencies. Provide theme options (light/dark mode) which often improves contrast choices.
• Syntax Colors: Use distinct colors for different JSON elements (keys, strings, numbers, booleans, null). These colors should also have good contrast against the background. Avoid relying *solely* on color to convey meaning.
• Formatting: Allow users to toggle between compact and pretty-printed (indented) JSON. Pretty-printing significantly improves readability.
• Line Wrapping: Long JSON lines that scroll horizontally are frustrating. Provide an option to wrap lines.

Font Size and Readability

Allow users to adjust the font size. Do not disable system font scaling. JSON keys and values can be lengthy, and providing larger text options is essential for readability.

• Scalable Text: Use scalable units (like `sp` or `dp` on Android, dynamic type on iOS) for font sizes.
• Readable Font: Choose a clear, readable font. Monospace fonts are common for code but ensure they are accessible and support readability features like distinct "l", "1", and "I".

Navigation and Interaction

Navigating complex, nested JSON structures on a small mobile screen requires careful design.

Collapsible Nodes

Implementing collapsible/expandable nodes (objects and arrays) is crucial for managing complexity.

• Clear Indicators: Use clear visual indicators (like arrows or plus/minus signs) for collapsible elements. Ensure these indicators are part of the touch target and are accessible to screen readers.
• State Persistence: Ideally, remember the collapse state when navigating back, or provide options to expand/collapse all nodes.
• Accessible Labels: The interactive element (the arrow or area to tap) should have an accessible label describing its state, e.g., "Expand object", "Collapse array".

Touch Target Size

Interactive elements, especially the tiny arrows or icons used for collapsing, must have sufficiently large touch targets (at least 44x44 CSS pixels).

Gestures

While gestures like pinching to zoom can be helpful for viewing very large structures, ensure that essential interactions (like expanding/collapsing) are also available via standard taps. Not all users can perform complex gestures reliably.

Keyboard Navigation and Assistive Technologies

Many mobile users, particularly those with motor impairments or using external keyboards, rely on keyboard navigation. Screen reader users rely on proper semantic structure and labels.

Screen Reader Support

The structure of the JSON viewer needs to be understandable by screen readers (VoiceOver on iOS, TalkBack on Android).

• Semantic Elements: Use semantic HTML elements if the app uses web views, or the equivalent native components with accessibility properties. For example, treat collapsible nodes like disclosure widgets.
• Labels and Roles: Provide meaningful labels for all interactive elements. Clearly indicate the role of elements (e.g., "object", "array", "string key", "number value").
• State Announcement: When a node is expanded or collapsed, the screen reader should announce the change in state (e.g., "object collapsed", "array expanded, 5 items").
• Content Description: For complex values (like nested objects/arrays), provide a concise description for the screen reader initially, allowing the user to expand for details. E.g., instead of reading out the entire nested structure, say "object, collapsed, 7 keys".

Keyboard Navigation

Ensure users can navigate through the JSON structure using standard keyboard commands (Tab, Arrow keys).

• Focus Management: Clearly indicate the currently focused element. Ensure focus order is logical (e.g., traverse keys and values sequentially, or allow moving into/out of collapsed nodes).
• Interactive Elements: Collapsible indicators and any other interactive elements must be reachable via keyboard focus and activatable using Enter/Space.

Magnification and Reflow

Users may use system-level screen magnification. The layout should reflow gracefully when zoomed, avoiding excessive horizontal scrolling. Line wrapping is crucial here.

Search and Interaction Aids

Searching within JSON is a key feature, and it needs to be accessible.

• Visible Search Input: The search bar should be easily located.
• Accessible Search Results: When search results are highlighted, the highlighting should have good contrast. Provide controls to navigate between results (e.g., "Next", "Previous"), which should be keyboard and screen reader accessible.
• Error Reporting: If the user enters invalid search syntax or the search fails, provide clear, accessible error messages.

Customization Options

Allowing users to customize the viewing experience can significantly improve accessibility for various needs.

• Theme Selection: Provide light, dark, and potentially high-contrast themes.
• Font Preferences: As mentioned, font size control is key. Allowing users to select specific accessible fonts could be beneficial.
• Indentation Level: Allow users to choose the indentation size for pretty-printed JSON.

Testing for Accessibility

Accessibility is not a feature you add at the end; it must be considered throughout development and tested thoroughly.

• Manual Testing: Test the app using system accessibility features:
  • Enable Screen Reader (VoiceOver/TalkBack) and try to navigate and understand the JSON structure.
  • Use system font scaling and magnification features.
  • Test with an external keyboard.
• Automated Tools: Use available accessibility scanners for mobile platforms (e.g., Accessibility Scanner for Android, Accessibility Inspector for iOS) to catch common issues like low contrast and missing labels.
• User Testing: Ideally, involve users with disabilities in your testing process.

Conclusion

Making a mobile JSON viewer accessible requires attention to detail in visual design, interaction patterns, and compatibility with assistive technologies. By focusing on clear presentation, flexible navigation, and robust support for screen readers and keyboard navigation, developers can create applications that are usable and helpful for a much wider audience. Prioritizing accessibility from the start leads to better design for all users.